A bit like a game we used to play. Turn your mates key off or hit their kill switch if they had one. All good fun till 2 mates got tangled up and both hit the road. We didn't play that game anymore.
This used to happen to me in Mountain-bike races, where there's no one to see.... it was mostly my "friends" who did it to me. As I was rubbish it didn't really matter
If your a professional racer its pretty poor form though.